Explosion protective apparatus



' April 1949- c. H. BARNARD ETAL 2,467,131

EXPLOSION PROTECTIVE APPARATUS Filed Nov. 8, 1945 I so INVENTORS AYTONH. BARNARD A PAUL s. DICKEY 5mm TTORNEY Patented Apr. 12, 1949 UNITEDSTATES PATENT OFFICE EXPLOSION PROTECTIVE APPARATUS Clayton H. Barnard,Cleveland, and Paul S. Dickey, East Cleveland, Ohio, assignors to BaileyMeter Company, a corporation of Delaware Application November 8, 1946,Serial No. 708,560

' 11 Claims. (Cl. 171-252) This invention relates to apparatus forprotecting against the ignition of explosive gases. It relates moreparticularly to means for purging a casing of explosive gases andcontrolling the operation of apparatus contained within the casing.

It is frequently necessary that apparatus having a tendency to igniteexplosive gases, be used in places where such gases are present. Forinstance, lt may be necessary that an electrically actuated meter beused in such a place for measuring some condition. The meter may beenclosed within a casing, but it is difilcult to seal the latter againstthe passage of gases to its interior. It may be necessary that thecasing be opened at times to make adjustments or to change recordingcharts, and then, if explosive gases are present, the casing will becomefilled with the gases and an explosion may take place unless some meansare provided for purging the gases from the casing before the circuitsfor the meter are completed.

A preferred form of our invention may include a pressure responsivemechanism which is operative to complete electrical circuits in thecasing only when the pressure in the latter exceeds the pressure at itsexterior by a predetermined amount. By providing a restricted escape forfluid within the casing and supplying to the latter a gaseous fluidwhich is free of explosives, there may be obtained a purging of thecasing and a gradual increase of the pressure therein to the desiredvalue. The pressure responsive mechanism may be made operative tocomplete the electrical circuits only when the pressure in the casinghas beenincreased to a value suflicient to force gases therefrom and hasbeen maintained at such value for a period of time sufficient to assurea complete purging of the gases. The pressurizing of the casing may beeiiected by supplying thereto an inert gas, such as nitrogen, or airfrom the atmosphere at a point where it is free of explosive gases.

An object of our invention is to provide means for purging a casing ofgases and controlling the operation of apparatus contained within thecasing. Another object is to provide means for pressurizing a casingwhich has restricted communication with its exterior and effecting theoperation of apparatus in the casing after the latter has beenpressurized. Yet another object is to provide for a casing havingrestricted communication with its exterior, means for supplying agaseous fluid to the casing, and means responsive to the pressures inthe casing for controll- 2 ing electrical circuits to apparatuscontained within the casing. Other objects will appear in the course ofthe following description.

There are shown in the accompanying drawing several forms which ourinvention may assume in practice.

In this drawing:

Fig. 1 is a perspective view of a meter with a portion of its casingbroken away to disclose a device operating in response to pressureswithin the casing and controlling the circuit for an elec-- tric motorcontained therein.

Fig. 2 is an enlarged vertical sectional view of the pressure responsivedevice shown in Fig. 1.

Fig. 3 is a schematic diagram of another form of control system for ameter casing and motor circuit.

Fig. 4 is a schematic diagram showing still another form of theinvention.

Referring to Fig. 1, it will be noted that there is shown a meter,generally designated I, having a casing portion 2 which is adapted to beclosed by a hinged door 3. Arranged within the casing portion 2 is abacking plate 4 for supporting a chart 6, which is adapted to be rotatedby any suitable means, not shown. A pen arm 8 moves over the chart 6 andis operatively connected to an electric motor l0 for actuation by thelatter in accordance with changes in the value of a condition beingmeasured. The spaces of opposite sides of the backing plate are incommunication with each other through spaces surrounding the driveconnections for the chart andthe pen arm, and may be in communication byreason of a loose fitting of the back plate within the casing. Thehinged door 3 does not fit the casing portion 2 so tightly when closedbut what some leakage takes place between the interior and exterior ofthe casing. There may also be some leakage between the interior andexterior of the casing along the connections'leading to the operatingparts of the meter. It will be seen that by reason of such leakages, anygases in the space surrounding the casing may gain admission theretoeven when the door is closed. When the door is opened to change thechart, the gases will readily gain admission to all parts of the casing.If the meter is being usedin a place where explosive gases are present,such gases will get into the casing and may be ignited by sparks fromthe electric motor or other portions of the electric circuit.

In order to purge the casing of explosive gases, it is proposed tosupply a pressure fluid to the interior of the casing until a suflicientpressure 3 is built up therein to cause any gases to leak to itsexterior. Means responsive to the casing pressures are provided forcontrolling the motor circuit so that an operation of the motor isobtained only when the desired pressure exists in the casing.

As shown in Fig. 1, a pressure responsive device i2 is arranged withinthe casing portion 2 and comprises casing members l4 and I5 clamped toopposite sides of a diaphragm IS. A conduit l1 leads from a source ofpressure fluid supply, such as a tank l8, through a wall of the metercasing to communicate with the space between the diaphragm and thecasing member i5. Ports 20 formed in the casing member l5 connect thespac at its inner surface in free communication with the interior of themeter casing so that the pressure fluid, which may be pure air or aninert gas, such a nitrogen, flows into the meter casing and builds up apressure therein equal to the pressure acting on the diaphragm IS. Amanually controlled valve 2| is provided for regulating the flow ofpressure fluid so that the pressure in the meter casing will reach intime the desired value. The space between the diaphragm and the casingmember I4 is subjected to atmospheric pressure by a conduit 23 leadingfrom the space to the exterior of the meter casing. A spring 24 actsbetween the casing member 14 and thediaphragm for opposing movement ofthe latter by pressures acting upon its opposite side. Fixed to thecasing member i5 and the diaphragm I6 at their sides adjacent each otherare electrical contact elements 25 and 26 which are normally in an openposition, but which are adapted to be closed when the diaphragm is movedagainst the action of the spring 24. Conductors 28 and 29 connect thecontact elements 25 and 26 in series with a solenoid winding 30 and to asource of power, such as a battery 3|. A plunger 32 actuated by thewinding 30 is connected to a switch 34 which controls the flow ofcurrent from lines 36, 31 to the motor Ill. The switch may be located ata point which is remote from the meter and free of explosive gases, or,if desired, it may be located close to the meter and be enclosed in afluid tight casing 38.

When the meter is placed in operation its door is closed so that thereis only a restricted communication between its interior and exterior.The valve 2i is then opened to supply pure air or an inert gas from thetank l8 to the space between the diaphragm l6 and the casing member l5.The air or inert gas then flows through the ports 26 to the meter casingand carries with it away from the contact elements 25, 26 any explosivegas which may be present. The flow of fluid to the meter casing causesthe pressure therein to increase until the fluid escapes from the casingat a rate equal to the supply. The spring 24 is designed so that thediaphragm is moved to close the contact elements 25, 26 when thepressure in the casing reaches approximately the maximum desired value.Closing of the contact elements results in an energization of thesolenoid winding 30 to close the switch 34 and supply current to themotor l0. As the pressure builds up in the meter casing, there will besome fluid escaping therefrom and carrying with it explosive gases. If asuflicient purging of the cas-, ing is not obtained before the pressurebuilds up to the value at which it closes the contacts 25, 26, a furtherdelay may be obtained by providing any suitable means which efiectsclosure of the line switch 34 after a predetermined period of time.

' or may be unrelated thereto.

It will be seen that a loss of pressure in the meter casing resultingfrom a failure of the pressure fluid supply or an excessive escape offluid from the casing, causes the contact elements 25, .26 to open anddeenergize the solenoid winding 30 so that the switch 34 opens and cutsofi the supply of current to the motor.

In Fig. 3 there is shown a meter like that of Fig. l but containingwithin its casing a pressure responsive device 40 which operates tocontrol a pilot valve 4| instead of contact elements for an electricalcircuit. The pilot valve is like that disclosed in the patent to Johnson2,054,464 and operates to control the flow of pressure fluid from asource of supply through conduits 42 and. 43 to a bellows 45 whichactuates the switch 34 in th lines 36, 31. The pilot valve has a valveelement 4'! which is connected to a diaphragm 43 of the device 40, andis movable by the diaphragm to a position connecting the conduit 42 incommunication with the conduit 43 leading to the bellows. In the normalposition of the diaphragm 48, the valve element is positioned to ventfluid from the bellows to atmosphere.

The fluid supply conduit 42 is also connected by a conduit 50 incommunication with the interior of the meter casing so that a pressureis built up therein for purging the casing and forcing the diaphragmagainst the action of the spring 24 to position the valve element. Byeffecting an operation of the line switch through fluid actuated meansrather than through an electrical circuit, there is avoided thepossibility of an explosion which might be caused by an inadequatepurging of the casing before the circuit was closed. The supply of fluidto the bellows may be made such that the line switch is not closed untila predetermined lapse of time after the pilot valve is positioned by thediaphragm, the time lapse being made suflicient to assure a completepurging of the casing before the motor is started.

In Fig. 4 there is shown an arrangement in which a pilot valve 52 likethe valve 4|, has a valve element 53 connected for operation by themotor in of a meter like that of Fig. 1. As described in the patent toJohnson 2,054,464 the valve element 53 is continuously vertically (inthe drawing) positioned by the motor l0 relative to the casing 52 toestablish in the pipe 56 a pneumatic loading pressure representative ofthe value of the variablewhos value is recorded by the pen 8 upon thechart 6. The pilot valve in this case is arranged within the metercasing and controls the flow of pressure fluid from a source of supplythrough conduits 55 and 56 to a fluid actuated valve mechanism 58 in aconduit 59. The valve 58 is shown as located in a pipe 59 forcontrolling the rate of flow of fluid therethrough.

The fluid flow through pipe 59 may contribute to the value of thevariable recorded by pen 8 This pilot valve, as described in the abovementioned patent of Johnson, permits a continuous restricted escape ofpressure fluid past its ends. The escaping pressure fluid causes apressure to be built up in the meter casing and in the casing of apressure responsive device l2 for efi'ecting completion of a circuit orthe operation of a pilot valve, as in Figs. 1 and 2, to close the lineswitch 34.

As a result of our invention there is provided improved means foreffecting the removal of gases 'from a casing and preventing theoperation of applied to a meter, it will be understood that it may beapplied to any chamber device and the control of other apparatus.

While there are described in this application several forms which ourinvention may assume in practice, it will be understood that these formsof the same are intended merely as illustrations and that the inventionmay be modified and embodied in various other forms without departingfrom its spirit or the scope of the appended claims.

What we claim as new, and desire to secure by Letters Patent of theUnited States, is:

1. The combination with a chamber device having restricted communicationbetween its interior and exterior and containing a power actuatedmechanism, of means for supplying power to said power actuatedmechanism, means for supplying pressure fluid continuously to theinterior of said chamber device, a pressure responsive device subjectedto the pressures in said chamber device, and means including an elementcontrolled by said pressure responsive device for controlling said powersupply means.

2. The combination with a chamber device having restricted communicationbetween its interior and exterior and containing a power actuatedmechanism, of means for supplying power to said power actuatedmechanism, means for supplying pressure fluid continuously to theinterior of said chamber device, and means for controlling said powersupply means, said last mentioned means including a device responsive tothe pressures in said chamber device and operative at a predeterminedmaximum pressure for initiating the supply of power by said power supplymeans.

3. The combination with a casing having restricted communication betweenits interior and exterior and containing electrical apparatus, of meansfor supplying pressure fluid continuously to said casing, a switch forcontrolling a circuit to said electrical apparatus, a pressureresponsive device subjected to the pressures in said casing, and meanscontrolled by said pressure responsive device and operating to efiect acontrol of said switch.

4. The combination with a casing having restricted communication betweenits interior and exterior and containing electrical apparatus, of meansfor supplying pressure fluid to said casing,

a switch 'for controlling a. circuit to said electrical operating at apredetermined maximum pressure for efiecting a closure of said switch.

5. The combination with a casing having restricted communication betweenits interior and exterior and containing electrical apparatus, of meansfor supplying pressure fluid to said casing, a switch for controlling acircuit to said electrical apparatus, a pressure responsive devicesubjected to the pressures in said casing, and an electrical circuit forcontrolling said switch, said electrical circuit including contactelements controlled by said pressure responsive device and a solenoidoperatively connected to said switch.

6. The combination with a casing having restricted communication betweenits interior and exterior and containing electrical apparatus, of apressure responsive device including a diaphragm arranged within saidcasing, means for subjecting one side of said diaphragm to casingpressure and the other side to exterior pressure,

means for supplying pressure fluid at a controlled rate to said casing,a circuit including a switch for supplying power to said electricalapparatus, a solenoid for controlling said switch, contact elementsadapted to be closed by said diaphragm when the pressure in said casingreaches a predetermined maximum value, and a circuit connecting saidsolenoid and said contact elements in series with a source of electricpower.

7. The combination with a casing having restricted communication betweenits interior and exterior and containing electric apparatus, oi apressure responsive device including a diaphragm arranged within saidcasing, means for subjecting one side of said diaphragm to casingpressure and the other side to exterior pressure, means for supplyingpressure fluid at a controlled rate to said casing, a circuit includinga switch for supplying power to said electric apparatus, a pressureresponsive device for controlling said switch, means for supplyingpressure fluid to said last mentioned pressure responsive device, andvalve means operatively connected to said diaphragm for controlling theflow of pressure fluid in said last mentioned pressure fluid supplymeans.

8. The combination with a casing having restricted communication betweenits interior and exterior and containing an electric motor, of means forsupplying pressure fluid to said casing, a pressure responsive deviceresponsive to the pressures in said casing, a circuit including a switchfor supplying current to said motor, pressure responsive means forcontrolling said switch, means for conducting pressure fluid relative tosaid pressure responsive means, and valve means operatively connected tosaid pressure responsive device for connecting said fluid conductingmeans selectively to a pressure fluid supply and to exhaust.

9. The combination with a casing having restricted communication betweenits interior and exterior and containing an electric motor, valve meansarranged within said casing and operatively connected to said motor,said valve means controlling the flow of pressure fluid from a source ofsupply to a fluid actuated device and passing a continuous restrictedflow of pressure fluid to said casing, a circuit including a switch forsupplying current to said motor, and means including a device responsiveto the pressures in said casing for controlling said switch.

10. The combination with a casing having restricted communicationbetween its interior and exterior and containing an electric motor, of apressure responsive device including a diaphragm connected at one sidein free communication with said casing and at its other side in freecommunication with the exterior of said casing, means for supplyingpressure fluid to said diaphragm at the side communicating with saidcasing, a circuit including a switch for supplying power to said motor,a solenoid for controlling said switch, and a circuit includin a contactelement connected to said diaphragm for controlling said solenoid.

11. The combination with a casing having restricted communicationbetween its interior and exterior and containing electrical apparatus,of means for supplying pressure fluid to said casin a switch forcontrolling a circuit to said electrical apparatus, a pressureresponsive device having opposed surfaces, one surface exposed to thepressure within the casing and the other surface exposed to the pressureat the exterior of the casing, yieldable means acting upon said devicefor opposing its operation by the pressure within the casing, and meansoperatively connected to said REFERENCES CITED device for controllingsaid switch, said last men- The following r ferences are of record inthe tioned means operating at a predetermined maxifi Of this Patent! mumpressure within the casing for effecting a. 5 vtmrrm) STATES PATENTSclosure of said switch.

I CLAYTON H. BARNARD. Number Name Date PAUL s. DICKEY. 2,021,454 LevinNov. 19, 1935

